Dick caught her in his arms and spoke such soothing words as came first to his tongue. “I am here to help you,” he said, “although my coming here is only the result of an accident. Tell me about yourself. What brought you here and how is it that you are alone?” “It was that scoundrel Mudd!” replied the girl. “He has held me a prisoner in this dreadful place since his tools captured me on the mountain night before last. They have a camp down here, Mr. Darrell. I’ve been a close prisoner until about an hour ago, when I managed to get away and--oh, oh! There comes that dreadful noise again! What is it? Oh, what is it?” In her excitement she clutched Dick’s arm and begged him to protect her, and there was nothing strange about her excitement either, for an awful bellowing was heard off on the lake, echoing and re-echoing back from the rocky walls of the cavern until the whole atmosphere reverberated with the frightful sound. But it did not disturb Dick a bit. He knew very well that it was only the Plesiosaurus. This underground lake then had its monster as well as the one above. Of course, Dick had given up the idea that there was only one P. D. He knew that there must be many and if Charley had only been safe with him he would have rejoiced in the discovery. As it was he hastily explained to Clara what the noise really meant and as the bellowing continued they stood there looking off on the lake watching for the Plesiosaurus to appear. “We may not see it at all,” said Dick. “There! It has stopped. No doubt it has gone under the water and--oh, Charley! Charley! This way! Here I am! It’s Dick! Hello! Hello!” Suddenly Charley’s shout was heard in the distance and Dick lost no time in answering. At the same instant there was a rushing sound on the water right in front of them and the same old monstrous head came up out of the lake. Clara screamed and threw her arms about Dick. Higher and higher the head was thrust up as the neck of the monster came out of the water. Then came the frightful bellow once more and the head of the monster came darting toward them. Flinging a protecting arm about Clara, Dick drew her hastily back and they ran for their lives. CHAPTER XIV. LOST UNDERGROUND. The Plesiosaurus made no attempt to come up out of the water. Once more it gave its strange cry and Dick, looking around, saw its huge back come up into view, and, with its long neck arched like a swan, it sailed away over the lake and was soon lost to view in the darkness. Dick and Clara had now stopped running and stood looking off over the lake watching the strange creature as it sailed away. “I ought to be ashamed of myself for being so timid, Mr. Darrell,” said Clara. “But I have had such a dreadful time that my nerves are all shaken. What is that creature? I didn’t suppose anything like it existed on earth.”